It is proposed to design complexes containing transition metals bound to simple macrocyclic ligand systems. These complexes will be used: (1) as models to examine the details of reaction mechanisms of general interest or which seem to be significant in complex biological systems; (2) in attempts to model in simple systems reactions of metallo enzymes which seem to have little or no precedent in simpler inorganic systems. Where possible reactions of the prosthetic groups of metallo enzymes will be examined under the conditions of the model reactions. BIBLIOGRAPHIC REFERENCES: G. J. Ferraudi and J. F. Endicott, "A Flash Photolytic Study of Low Energy Homolytic Processes in Methyl Cobalamin," J. Amer. Chem. Soc., 99, (1977). In press. J. F. Endicott, J. Lilie, J. M. Kuszaj, J. M. Kuszaj, B. S. Ramaswamy, W. G. Schmonsees, M. G. Simic, M. D. Glick, and D. P. Rillema, "The Trans-Influence and Axial Interactions in Low Spin, Tetragonal Cobalt(II) Complexes Containing Macrocyclic and/or Cyano Ligands. Pulse Radiolytic Studies in Fluid Solution, Electron Paramagnetic Spectra at 77 degrees K, and Single-Crystal X-ray Structures," J. Amer. Chem. Soc., 99, (1977). In press.